Electric valve circuits



June l3, 1 944. A, H. MITTAG ELECTRI C VALVE CIRCUIT Filed May 30, 1942 2 Sheets-Sheet l Fig.5. 38

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I i a, I K l7 9 m I Inventor: Albert H. Mittag,

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June 13, 1944. A, H. MlTTAG 2,351,062

ELECTRIC VALVE CIRCUIT Filed May 30, 1942 2 Sheets-Sheet 2 Inventor: Albert H. Mittag,

by firm/ 4 xiv/*1 His Attorney.

Patented June 13, 1944 ELECTRIG VALVE CIRCUITS Albert H. Mittag, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application May 30, 1942, Serial No. 445,177

5 Claims.

My invention relates to electric valve circuits and more particularly to control or excitation circuits for electric valve apparatus of the type employing an ionizable medium capable of supporting an arc discharge.

This application is a continuation-in-part of my copending patent application Serial No. 413,232, filed October 1, 1941, entitled Electric control circuit and which is assigned to the assignee of the .present application. The present invention is in the nature of an improvement on the circuit disclosed and claimed in the copending Lord application ,Serial No. 466,603, filed November 23, 1942, entitled Electric Circuits, and assigned to the assignee of the present invention.

In the control of electric valve apparatus which employs a gas or a vapor as the ionizable medium, it is frequently desirable to provide means which render the electric valve means conducting at precisely determinable instants of time. In those arrangements which use electric valves comprising ignition means, such as immersion-igniter control members, in order to relieve the duty imposed on the control members and to increase thereby the life of the electric valve means, .it has been found desirable in some instances to provide auxiliary oradditional electrodes to transfer the ignition current from the control members as soon .as are discharges .are initiated. In accordance with the teachings of my invention described hereinafter, I provide new and improved circuits for application to electric valve means of this type and wherein precision and reliability in the starting of the electric valve means is assured.

It is anobject of my invention to provide new andimproved electric valve circuits.

It is anotherobject of my invention to provide newand improved control or excitation circuits for electric valve means.

It is a further object of my invention to provide new and improved control or excitation circuits for electric valve apparatus wherein the duty imposed on the starting or ignition .means of the electric valve meansis substantially reduced and whereby the desired flexibility and reliability of control and starting are not sacrificed.

Briefly stated, in the illustrated embodiments of my invention I provide new and improved excitation circuits, such as electric impulse generators, for transmitting impulses of current to are ignition means such as immersion-igniter control members, and wherein means are provided for relieving the dutyimposed on the arc ignition means. In addition, I provide means for assuring the reliability of the starting of the electric valve means and the assumption of load thereby by providing apparatus which supplies to the relieving anodes of the electric valve apparatus voltages of desired magnitude and phase position to maintain the medium of the electric valve means in an ionized condition for desired intervals of time after the initiation of arc discharges occasioned by the proper energization of the arc ignition means.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims. Fig. 1 diagrammatically illustrates an embodiment of my invention as applied to a bi-phaserectifier, and Fig. 2 represents certain operating characteristics thereof. Fig. 3 diagrammatically illustrates another embodiment of my invention as applied to a quarter-phase electric valve translating system, and Fig. 4 represents a still further modification of the arrangement shown in Fig. 1.

Referring now to the embodiment of my invention shown in Fig. 1, I have there illustrated my invention as applied to an electric valve converting system which may be a bi-phase rectifier in which energy is transmitted from an alternating current supply circuit I to a direct current load circuit comprising a positive conductor 2 and a negative conductor 3. The electric valve translating apparatus comprises a transformer 4 and a pair of electric valve means 5 and 6 which are of the type employing an ionizable medium, such as a gas or a vapor, and each of which includes an anode 1, a cathode of the self-reconstructing type such as a mercury pool cathode 8, are ignition means such as an immersion-igniter control member 9 which may be associated with the cathode 8, and a relieving anode Ii). The immersion-igniter control members 9 are constructed of a material such as boron-carbide orsilicon-carbide having an electrical resistivity whichis substantially high compared with that of the mercury of the associated pool, andwhen properly energized by transmitting theretoa current of predetermined minimum value establish cathode spots on the surface of the associated Qoland consequently initiate arc discharges by ioni i g the medium Which is mercury vapor when the mercury pool is employed.

Inorder to energize the immersion-igniter control members 9 alternately and to cause electric valvemeans Sandi to transmitcurrent alter- Considering now more particularly the excitation circuit H, I provide a capacitance l2 which is connected to be charged from the alternating current circuit I through a linearinductive reactance l3 and a phase shifting circuit. The

phase shifting circuit may include a capacitance 14, an inductance l5 and a variable impedance element such as an inductance l 6 of the saturable type. The inductance [6 may be provided with a control winding I! which may be variably energized or adjustably energized from a source of direct current I8 through a current controlling resistance l9. As the voltage of capacitance [2 during each half cycle attains a predetermined value, the inductive reactance of a saturable inductance 2U abruptly decreases effecting discharge of the capacitance l2 through a circuit including an impedance element 2| and a resistance 2B. In this manner, once during each half cycle an impulse of voltage is produced across the terminals of impedance element 2| and these impulses of voltage are used to energize the immersion-igniter control members 9.

The impedance element 2| may take the form of an inductance, such as an auto-transformer. The terminal connections 22 and 23 are connected to control members 9 of the electric valve means 5 and 6 through unidirectional conducting devices 24 and 25, respectively. An intermediate or neutral connection is connected to a common juncture of the cathodes 8.

As a means for assuring positive conduction of electric valve means 5 and 6 after the initiation of arc discharges by the energization of immersion-igniter control members 9 and to maintain the medium in an ionized condition for a predetermined portion of each positive half cycle of anode-cathode voltage, or during half cycles of predetermined polarity, I provide means for supplying to the relieving anodes l0 timed voltages, such as periodic voltages of predetermined phase displacement, to assure this condition of conductivity. For example, I may provide a transformer 21 energized from the alteralternately. The times of the occurrence of these impulses of .voltage are controlled or adjusted by means of the phase shifting circuit including the saturable inductance l6. By adjusting the current transmitted to control winding II, the voltage applied to excitation circuit H is adjustable and consequently the time of production of the impulses of voltage across impedance 21 is also controlled.

In this manner the magnitude of the voltage applied to direct current circuit including conductors 2 and 3 is also controllable, the voltage increasing as the time of occurrence of the impulses is advanced towards the beginning of the positive half cycles of appliedanode-cathode voltage and decreasing as the time of the impulses is retarded.

nating current circuit I through a phase shifter and comprising secondary windings 28 and 29 which are connected between the excitation circuit II and relieving anodes It] or electric valve means 5 and 6, respectively. More particularly, windings 28 and 29 are connected between the terminal connections 22 and 23 and relieving anodes H3. The voltages supplied to the relieving anodes l0 serve to extend or tail-out the voltage applied to the relieving anodes 10, thereby assuring the maintenance of arc discharges within the electric valve means 5 and 6 for substantially the entire positive half cycles of applied anode-cathode voltage.

-.The operation of the embodiment of my -in vention shown in Fig. 1 will now be explained. Excitation circuit H transmits impulses of current alternately to the immersion-igniter control members 9 of electric valve means 5 and 6, there by rendering the electric valve means conducting As soon as are discharges are initiated within each of the electric valve means 5 and 6 by the transmission of unidirectional impulses of current to the control members 9, a substantial portion of the excitation current supplied by circuit H is transferred to the relieving anodes Hi thereby relieving the duty imposed on control members 9. Due to the nature of the impulses of voltage produced by excitation circuit H, which are of relatively short duration, the arc in the absence of conduction of current between the anode and cathode will not be maintained for a period greater than the duration of the impulses. For example, referring to the operating characteristics shown in Fig. 2, the curve A represents the nature of the voltage supplied to the immersionigniter control membersS. The sharp peak a represents the initial portion of the peak of excitation current which is transmitted to the immersion-igniter control member 9, and at time b the greater portion of the excitation current is transferred to the relieving anodes l0. At time c it will be appreciated that the arc-maintaining function of the relieving anode to would be discontinued inasmuch as the impulse of voltage derived from excitation circuit II has decreased to a value which is insufiicient to maintain an arc discharge. However, the voltages supplied by secondary windings 28 and 29, and one of which may be represented by curve B, serve to supply to the relieving anodes of the electric valves, such as electric valve 5, a voltage which assures the maintenance of the medium in an ionized condition for substantially electrical degrees after the initiation of the discharge by the energization of control member 9. It will be understood that a similar function is accomplished by winding 29 which is associated with relieving anode ID of electric valve means 5. In this manner, a positive means is provided for assuring the maintenance of the medium in an ionized condition and assuring that the electric valve means will assume load, thereby obviating many of the difliculties incident to the prior art arrangements.

A further modification of my invention is shown in Fig. 3 as applied to a quarter-phase electric valve translating system, such as a quarter-phase rectifier, for transmitting energy from a three phase alternating current circuit 30 to a direct current load circuit including conductors 3| and 32. The translating apparatus includes transformers 33 and 34 connected in the conventional Scott or T-connection and having secondary windings 35 and 36 provided with neutral connections 31 and 38, respectively. The neutral connections 31 and 38 may be connected to the negative conductor 32 of the direct current circuit through an interphase transformer 39. Electric valve means 4fl43 are connected to the secondary windings 35 and 36 and are of the type employing an ionizable medium each including an anode 44,- a cathode 45, an immersion-igniter control member 45 and a relieving anode 41. I provide excitation circuits 48 and 49 for transmitting impulses of current to the control members of electric valve means 40, 4| and 42, 43, respectively. These excitation circuits are similar in construction and arrangement to the excitation circuit ll of Fig. 1, and corresponding elements have been assigned like reference numerals.

In order to maintain an equal division of load between the electric valve means 40, 4| and 42, 43, I provide load division or load equalizing means which may comprise a resistance 50 which is connected in circuit with control windings I! of the inductances I 5 in excitation circuits 48 and 49. The polarity of the voltage appearing across terminals 5| and 52 of resistance 50 is controlled in response to any variation in the desired division of load, and thereby varies the phase of the voltage impressed on the excitation circuits to re-establish the desired load division. Certain aspects of this type of load balancing or load dividing arrangement are disclosed and claimed in a copending patent application of Ernst F. W. Alexanderson Serial No. 408,779, filed August 29, 1941, and which is assigned to the assignee of the present application, The selective energization of the resistance 50 in response to the division of load between the two groups of electric valve means 40,. and 42, 43 may be obtained by employin transformers 53 and 54 having primary' windings 55, 56 and 51, 58, respectively, which are energized in response to the current transmitted by electric valve means 40-43. Full wave rectifiers 59 and 60 are connected to secondary windings BI and 62 and are poled to transmit current in opposite directions through resistance 50.

Transformers 63 and 64 are connected to excitation circuits 48 and 49 and the relieving anodes 41 in a manner similar to transformer 21 of the arrangement shown in Fig. 1, and provide alternating voltages of predetermined phase relation to maintain arc discharges for predetermined intervals during each cycle of anode-cathode voltage.

The arrangement of Fig. 3 operates to transmit unidirectional current to the load circuit from the alternating current circuit 30. The magnitude of the voltage impressed across the load circuit may be adjusted by means of resistance l9. After the initial adjustment, the system perates to maintain a predetermined division of load between the two groups of electric valves.

The excitation circuits 48 and 49 and the transformers 63 and 54 cooperate to supply impulses of current to the electric valve means 40-43 to render the electric valves conducting in a predetermined order. The electric valves in each pair conduct current alternately during 180 electrical degree intervals, each valve conducting only 90 degrees with any one valve of the other group.

So long as the load transmitted by the respective groups of electric valves is equal, the connections and 52 are maintained at the same potential. If one group, however, tends to assume a larger portion of the load, a potential difference will be established between connections 5! and 52 by virtue of the operations of transformers 53, 54 and rectifiers 59 and 60 to decrease the current to one of the control windings I! and to increase the current transmitted to the other control winding, thereby assuring or controlling the phase of the voltages supplied to the excitation circuits 48 and 49 and re-establishing the desired or equal distribution of load.

I'ne embodiment of my invention shown in Fig. 4 is similar in many respects to the arrangement shown in Fig. 1, and corresponding elements have been assigned like reference numerals. In the arrangement of Fig. 4, the supply circuit is a polyphase alternating current supply circuit 65 and a phase shifting means, such as a rotary phase shifter 66 having primary windings 61 and a secondary winding 68, is employed. In this arrangement, the excitation circuit II is energized from terminals 59 and 10 of the secondary winding 58, and the transformer H which supplies the arc sustaining voltages to the relieving anodes I0 is derived from terminals 12 and 13 which are displaced substantially electrical degrees relative to the voltage applied to the excitation circuit II. It will be noted that secondary winding 14 of transformer 1| is connected across terminals 22 and 23 of the impedance element 2 I, or connected directly in circuit with the relieving anodes ID.

The system shown in Fig. 4 operates in substantially the same manner as that explained above in connection with the arrangement of Fig. 1. Transformer ll supplies the voltage to the relieving anodes H) to maintain arc discharges within the electric valve means for predetermined intervals of time after the initiation of the discharges occasioned by the proper energization of control members 9.

While I have shown and described my invention as applied to particular systems of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathode, an immersion-igniter control member associated with said cathode and a relieving anode, excitation means including the common terminal connected to said immersion-igniter control member for supplying thereto impulses of current to initiate are discharges and to energize said relieving anode, and means connected between said common terminal and said relieving anode for supplying to said relieving anode timed impulses of voltage to maintain the arc discharges between said relieving anode and said cathode for predetermined intervals of time after each energization of said control member.

2. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathode, an immersion-igniter control member associated with said cathode and a relieving anode, excitation means including the common terminal connected to said immersion-igniter control member for supplying thereto impulses of current to initiate arc discharges and to energize said relieving anode, ,and means connected between said common terminal and said relieving anode for supplying to said relieving anode an alternating voltage of predetermined phase position relative to the time of energization of said control member to maintain arc discharges between said relieving anode and said cathode.

3. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of electric valve means each having an anode, a cathode, arc ignition means and. a relieving anode, an excitation circuit for transmitting impulses of current alternately to said arc ignition means and comprising a capacitance, an auto-transformer, having terminal connections and a connection intermediate said terminal connections and a nonlinear inductive reactance for discharging said capacitance through said autotransformer, the terminal connections of said auto-transformer being connected to the arc initiatin means of the pair of electric valve means and the intermediate connection being connected tosaid cathodes, and means for impressing across said auto-transformer an alternating voltage of predetermined phase displacement relative to the voltage applied to said excitation circuit.

4. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of electric valve means each including an anode, a cathode, arc ignition means and a relieving anode, phase shifting means energized from said alternating current circuit, an excitation circuit for transmitting impulses of current to the arc ignitionrmeans of the pair of electric valve means to render the electric valve means conducting alternately and comprising an impedance element and means for transmitting an impulse of current through said impedance element during each half cycle of voltage of said alternating current circuit, means for connecting the relieving anodes to points of said impedance element of instantaneous different polarity, and means energized from said phase shifting means for supplying to said relieving anodes alternating voltages of predeterminedphase relation with respect to the impulses of current supplied to the arc ignition means to maintain arc discharges between associated cathodes and relieving anodes after the initiation of arc discharges occasioned by the energization of the associated ignition means.

5. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of electric valve means each including an anode, a cathode, arc ignition means and a relieving anode, phase shifting means energized from said alternating current circuit, excitation means energized from said phase shifting means for transmitting impulses of current alternately to the arc ignition means of the electric valve means and including an impedance element, means for connecting the relieving anodes to the impedance element, and means energized from said phase shifting means for impressing on said relieving anodes periodic voltages having a substantially quadrature relation with respect to the voltage applied to said excitation means.

ALBERT H. MI'I'IAG. 

